The present invention relates to a lubricant supply limiting device and to a servo pressure controller for use with the device.
In a lubricant supply limiting device of the type known from DE Patent 3,637,851, the adjustment member of the servo pressure controller is subjected to the action of a compression spring acting as the actuator, to thereby ensure that the variable throttle maintains the pressure difference established by the fixed throttle so as to ensure a constant lubricant flow independently of upstream and downstream pressures. For adjusting the lubricant flow to varying requirements at specified lubrication points, the lubricant flow can be switched between several fixed throttles, or one or more fixed throttles may be used at the same time. The fixed throttle or throttles used at any given time determines--or determine--the pressure difference and thus the lubricant flow which is maintained constant by the variable throttle of the servo pressure controller. The variation of the lubricant volume flow requires the employ of a considerably complicated construction. In addition, the variation of the volume flow occurs incrementally, so that it may not always be possible to accurately adjust the volume flow to the requirements of specified lubrication points.
Although it would be possible to avoid this incremental adjustment of the volume flow by the employ of a continuously adjustable fixed throttle in a flow control valve having a fixed throttle and a servo pressure controller--as is common use in the field of hydraulics--, with an actuator solenoid for adjusting the fixed throttle, the pressure difference over the fixed throttle is usually of a magnitude requiring the application of excessive adjustment forces. It is moreover difficult to reliably hold the fixed throttle at the selected adjustment position.